Various machines include implements that are raised and lowered to perform desired tasks. For example, machines like skid steer loaders may include a bucket, fork, or other implement that is raised and lowered to assist in transferring material between desired locations. In many cases, such implements are coupled to a frame of the machine by a lift arm assembly that serves to control the movement of the implement between the lowered and raised positions.
FIG. 1 shows a conventional skid steer loader 100 including a lift arm assembly 110. The conventional lift arm assembly 110 may include two arms 112 pivotably coupled to a frame 120 of the skid steer loader 100. An implement 130 may be connected to the front ends of the arms 112. An actuator 140 may be connected at one end to the lift arm assembly 110 and at another end to the frame 120. The actuator 140 may be controlled to rotate the lift arm assembly 110 about the pivot connection between the arms 112 and the frame 120, thereby moving the implement 130 between raised and lowered positions.
The conventional lift arm assembly 110 may be heavy, and costly and difficult to assemble. For example, a pair of lift arms for a skid steer loader is described in Japanese Patent Publication No. JP 2007-254986 (“the JP986 publication”) to Endo et al. The JP986 patent describes a pair of lift arms that include portions that are formed out of sheet metal or plate steel, and portions that are formed of cast steel. The portions that are formed from plate steel are formed by bending and welding together two or more sections of plate steel to form an arm with a cross-section that tapers along the length of the arm. The plate steel is cut into complex shapes to form the various features provided on the lift arms, such as portions for connecting to the hydraulic cylinders that control the movement of the lift arms. Also, the sections of plate steel for each lift arm form a seam where the sections of plate steel are joined and welded along the length of each lift arm. As a result, the lift arms of the JP986 publication that are formed from plate steel are heavier due to the weight and greater total length of the welds, and are more costly and difficult to assemble.
The disclosed lift arm assembly is directed to overcoming one or more of the problems set forth above.